Weather resistant films are used for various purposes in decorative construction materials. In particular, the weather resistant films are widely used for building exteriors where weather resistance is important. Currently, although the weather resistant films are mainly acrylic films, an attempt to introduce a fluorine resin into an upper layer is being made with increasing demand for weather resistance.
KR 2011-0007252 discloses a fluorine resin-stacked acrylic resin film for interiors and exteriors of vehicles, U.S. 2008/0293837 discloses an acrylic resin composition including PMMA/impact modifier/PVDF as main components, and U.S. 2010/0189983 discloses a highly weather resistant film using a polymerizable UV stabilizer and PMMA/PVDF.
Such various attempts are aimed at improving weather resistance of an overall film using excellent weather resistance of PVDF. In addition, due to high price of PVDF, it is extremely important to maximize capabilities of the film with a minimized amount of PVDF. To achieve this, coextrusion is mainly used.
An A/B type coextruded film is mainly used. In a lot of cases, an upper film is composed of a PVDF single layer or a PVDF/PMMA blend, and a lower film is composed of a PMMA/impact modifier blend. However, although known to exhibit compatibility, the PMMA/PVDF blend is known as having some limits in transparency, adhesion and the like due to crystallization properties of PVDF.